(1) Field of the Invention
The present invention relates to a closed-loop, vapor cycle, turbine systems that generate rotational power by absorbing energy from a high velocity, vaporized, working fluid.
(2) Description of Related Art
Power generation by vapor cycle turbine engines, using steam or other fluid vapors under pressure, has been a common practice for many decades. Systems having such turbine engines are typically comprised of a vapor generator for vaporizing the working fluid, a turbine, responsive to the vaporized working fluid produced by the vapor generator and producing work, and a condenser for condensing the expanded vaporized working fluid exhausted from the turbine and producing condensate that is returned to the vapor generator by a pump.
The turbines in practical use are typically of the impulse or reaction type and are divided into two broad categories, axial and radial flow. Both axial and radial flow turbines require a high quality, high velocity vapor which is distributed to the blades found in the turbine structure. For these bladed turbines, variations of vapor density result in an unbalanced mass flow passing through the rotating turbine which is undesirable for engine operation.
The drag turbine is a less common category of impulse turbine of which there are two general variations. In the first, high velocity vapor is directed, by a nozzle, to flow radially from the outer edge of a series of uniformly spaced, smooth disks compelling them to rotate about a central axis through the action of viscous drag. In a second variation, high velocity vapor is directed, by a nozzle, to flow tangentially against the smooth outer or inner surface of a cylindrical structure compelling it to rotate about a central axis, again, through the action of viscous drag. Both types of drag turbine do not require uniformly distributed flow and are highly tolerant of low quality vapor.
For bladed turbines, variations of vapor density result in an unbalanced mass flow which creates vibration that can lead to catastrophic failure of the turbine and its associated support structure. The variations of vapor density are attributable to variations in vapor quality localized within the vapor flow. Liquid droplets contained within a low quality vapor cause surface erosion of the delicate turbine blades. The erosion shortens the useful life of the blades and results in the turbine becoming statically unbalanced. Therefore, to achieve maximum life from a bladed turbine, the working fluid vapor entering and exiting the turbine must be in a high quality, non-condensing state. In a conventional closed loop power cycle, a condenser must be used to eject the latent heat of vaporization from the working fluid, returning the fluid to the liquid state for reuse in the cycle.
For a closed loop power system employing a bladed turbine, the necessity of a high quality vapor requires that the condenser eject a larger amount of waste heat from the vapor than would be required if the turbine could tolerate a low quality, condensing vapor flow. The requirement of the condenser to eject this larger amount of waste heat, results in a reduction of the overall thermal efficiency of the engine. Furthermore, the physical size and weight of the condenser, along with its associated pumps and plumbing, is a major impediment to the use of the closed loop power system in automotive and aerospace applications. Size, weight and overall thermal efficiency are principal design considerations in power systems developed for these applications.
Therefore, what is needed, and what the present invention provides, is a means such that the working fluid exiting the turbine is in the fully condensed liquid state. Employing such means returns the working fluid vapor to the liquid state within the turbine and entirely eliminates the need for a heat exchange condenser, and its associated pumps and plumbing.
Accordingly, the inventive turbine is able to tolerate a fully condensing working fluid flow while providing a unique mechanism, for returning the working fluid to the vapor generator without the need of a condenser or additional pumps.